This invention related generally to the digital manipulation of a continuous time domain sample that is to be sampled in a digital oscilloscope, and more particularly to a digital filter that is capable of increasing the bandwidth of the sampling system beyond the bandwidth range achievable in an analog system.
The present state of the art deals with an attempt to increase bandwidth based upon the assumption that only analog manipulation techniques for modifying a signal to improve the bandwidth characteristics of an apparatus are possible. Other digital techniques are seen as manipulations of the signal that change the output result of the system. This results in a design methodology in which analog design engineers painstakingly design to the best of their ability analog circuitry that has high bandwidth, flat frequency response, good pulse response and is noise-free.
In many cases, these designs are extremely complicated, particularly in the design of a digital oscilloscope. Some reasons for this difficulty are:                1. There is a wide variation in the gain of the front-end, sometimes approaching 60 dB of dynamic range.        2. The signal is typically distributed to multiple Analog/Digital Converters (ADCs) in order to boost sample rate. This distribution is through buffers that tend to decrease the bandwidth of the system.        3. High bandwidth/high sample rate oscilloscopes typically use the absolute best of present electronics technology and are therefore being pushed to the limits of the hardware.        4. Bandwidth, noise, and pulse-response are a set of conflicting requirements that must be reconciled.        
What makes things worse is that even upon observing and confirming the existence of problems with the bandwidth, flatness, pulse-response, and noise performance in the system, little can often be done to rectify the situation. This is because circuits designed to fix such problems are often not practically realizable.
Therefore, it would be beneficial to provide an improved Digital Signal Processing (DSP) method and apparatus capable of surgically dealing with lack of bandwidth, while offering some additional control of the pulse-response and flatness, and thereby decreasing the overall noise of the system as well.